Voltage indicating device



Oct. 5, 1937. 'r. E. FOULKE VOLTAGE INDICATING DEVICE Filed Oct. 15, 1955 INVENTOR Ted E. Foulk.

I 35 1M TTORNEY Patented 06 5,1937 2,094,645 v A UNITED STATES PATENT OFFICE VOLTAGE INDICATIN G DEVICE Ted E. Foulke, Nutley, N. L, assignor to General Electric Vapor Lamp Company, Hoboken, N. 3., a corporation of New Jersey Application October 15, 1935, Serial No. 45,128 2 Claims. (01. 175-183) The present invention relates to voltage indicating device intended for use with relatively cating devices and particularly to the use of elechigh voltage circuits, tric gaseous discharge devices to indicate poten- Fig.2 is a fragmentary sectional view of the detial diiferences. vvice of Fig. 1 showing the gaseous discharge lamps 5 A particular object of the invention is to protherein, and j 5 vide a simple and sturdy device which will indi- Fig. 3 is a. schematic wiring diagram showing cate by the length of a line of light the approxlthe electrical connections to these lamps. mate relative potential of an electrical conductor As shown in the drawing my novel voltage v to ground or another conductor. A further obmeasuring device has a housing consisting of a ject of the invention is to provide a device of this long fiber or other suitable insulating tube l with 10 type using a plurality of gaseous electric disa handle 2 at one end thereof and a conical concharge devices to produce the line of light. Still tact cap 3 at the other end thereof. Said tube other objects and advantages of the invention will I has an elongated opening 0 therein beneath appear from the following detailed specification which there is positioned a series of cathode glow or from an inspection of the accompanying drawlamps 5, 6, l, 8, 0, i0 and H. As illustrated these 15 ing. lamps are of the type disclosed in my Patent No.

The invention consists in the new and novel 1,965,585, granted July 10, 1934, but it is to be unstructure which is hereinafter .set forth and derstood that various other types and sizes of claimed. I V 7 these gaseous discharge lamps may be substituted A simple and sturdy voltmeter is often desired therefor if desired. Said lamps are equally spaced 20 for use in testing high voltage circuits. since along the opening d and are so arranged that such a device must be readily portable it is detheir electrodes can be clearly seen through said sirable that it should be both light in weight and opening, a y le supp rtin m ans (n t devoid of moving parts. It is likewise desirable Shown) be us d to eta t e a ps in the dethat such a device should have an extended range, sired p i n- Within Said tube i there is a P 25 SO as to be usable with any of the voltages comtentiometer i2 having a resistance of the order of monly encountered. In addition it must be rea- 55,000 ohms which is connected in series with a sonably accurate and above all certain in its indlresistance 43 0f the Order Of e The cation, especially where high voltage circuits are free end of said potentiometer is connected to being tested, since failure of the device might easthe grounded d M wh h xt n out through 30 ily lead to the death of a lineman through-touche Suitable Opening in the e W e t e ee ing what-appeared. to be a dead wire t the end of the resistance It is connected to the consame time it is essential that the device should be met p 3. A r r t nce H is c nnected in relatively inexpensive series with a switch it across the potentiometer I have now discovered that all of these requiresaid resistance having a value o t order of 35 ments are fully met by the novel use of a plurality 53,000 Ohms, whereby the Voltage p across Said of electric gaseous discharge devices connected potentiometer is cut in f e S d w t s across a potentiometer in a unique manner. With Closed, the range of the instrument being thereby this novel structure the breakdown potential of doubledthese devices is utilized to measure the applied The p 518 eelmeeted in e es w th a ballast 40 potential, more of the lamps lighting with higher resistance ll of the order of 450,000 ohms across potentials, the efiect being that of a line of light the entire potentiometer l2, this resistance, as whose length increases as higher potential is ap- Shown. in f m d fr m carbon impr nated plied. Due to this novel use of a plurality of paper. W th t 'va u s given above f r the valamps an element of safety is introduced since in usres sta ces approximately 60 v ts W b 45 every case except where only one lamp is lighted impressed across said lamp 5 when a potential an indication of the approximate voltage is given difierence oi. 2,000 volts exists between the cap :3 even though one of the cathode glow lamps has and ground with the switch l6 open, or 4,000 been totally destroyed. Hence there is little opvolts with the switch It closed. Since this is equal portunity for a live line to be mistaken for a dead to or slightly above the breakdown potential of 50 one, with perhaps fatal results. the lamp 5 this lamp will light under these con- For the purpose of illustrating my invention I ditions. The lamp 6 is in turn connected in series have shown a preferred embodiment thereof in with a somewhat smaller resistancem across apthe accompanying drawing, in which 1 proximately two-thirds of the potentiometer I2,

Fig. 1 is an elevational view of a voltage indiwhereby the voltage on said lamp 6 is suflicient 55 to light it when the applied potential is 3,000 volts. The remaining lamps 1, 8, 9, I0 and II are similarly connected across decreasing fractions of the potentiometer I2 in series with impedances I9, 20, 2 I, 22 and 23, respectively. These fractions are so chosen in the present case that successive lamps light up with each increase of a thousand volts, and the tube l is calibrated accordingly. The indicated values are, of course, doubled when the switch I6 is closed. The resistances II to 23 are preferably graduated in value so that the current taken by each of the lamps 5 to II is the same when all the lamps are lighted. Thus the line of light is uniform in intensity throughout its length, but varies in length and in brilliancy with the applied potential.

The opening 4 is closed with a glass 24, which is preferably ruby in color where neon lamps are employed. -This glass tends to increase the illusion of a line of light, and likewise due to its color serves to assist in reading the indication in daylight. Where desired, of course, additional screening, means, such as a black plate used as a background, may be used to cut down the extraneous light received by the observer from around the lamps, so as to increase the contrast and thus still further facilitate the reading of the instrument.

In the use and operation of this device the lead I4 is connected to ground and thecontact cap 3 then applied to 'the conductor 25 whose potential to ground it is desired to measure. With the switch IS in the open position the lamps 5 to II will light up, provided the potential of the conductor 25 is 2,000 volts or more, in accordance with the potential, the lamp 5 lighting up at approximately 2,000 volts, and one additional lamp lighting for each additional increment of 1,000 volts. When the switch I6 is closed these values are doubled.

With this novel arrangement an element of safety is introduced through the plurality of lamps employed. Thus supposing the lamp 6, for example, should be rendered inoperative for any reason. The lamp 5 would still operate and show that the potential was at least 2,000 volts, while if the potential was 4,000 volts or more there would be merely a darkspace in the line of light, the operator thus being instantly notified that the lamp 6 was inoperative, so that there is little opportunity for the operator to mistakenly assume that the conductor 25 is dead, due to failure of the discharge devices.

With the arrangement shown the high voltage is, of course, entirely confined to the end of the tube l which is remote from the handle 2, nothing but low voltage being applied to the lamps, while the switch it is grounded, so that there is no hazard to the operator in handling and operating the instrument, even on potentialsas high as 16,000 volts. Likewise the series resistance I3 is so high that no hazard would exist even; if the ground connection l4 should be opened by accident or otherwise.

This novel device is extremely light and portable, and is singularly rugged and immune fronf damage as a result of handling, due to its lack of moving parts. The lamps 5 to II are likewise extremely sturdy and withstand without dimculty exceedingly rough handling, far beyond anything they will normally encounter in this class of service. The device is likewise extremely simple and inexpensive, as compared to the devices now in use for measuring these high potentials. In addition this novel device not only has an unusually large voltage range, but also can tolerate large excess voltages without damageto the device.

While I have described my invention by reference to a particular embodiment thereof which has been found to give exceptionally good results it is to be understood thatit is not limited thereto, but that various omissions, substitutions and changes, Within the scope of the accompanying claims, may be made in the structure shown and described without departing from the spirit of my invention.

I claim as my. invention:-

1. A voltage measuring instrument comprising, in combination, an insulating tube having a contact on one end thereof, a potentiometer within said tube and connected with said contact, a plurality of electric gaseous discharge lamps having a substantially fixed breakdown potential within said tube and connected across different fixed fractions of said potentiometer, said fractions being so graduated that successive lamps light up as a linear function of the voltage drop in said potentiometer, said lamps being located behind a translucent portion of said tube and arranged sequentially whereby the illumination of successive lamps gives the illusion of an increasing line of light, a scale on the face of said tube to calibrate said line of light, and a resistance between each individual lamp and said potentiometer, said resistances being so varied in value that the current through each of said lamps is substantially the same when all of said lamps are operating.

2. A voltage measuring instrument comprising, in combination, an insulating tube having a contact on one end thereof, a potentiometer within said tube and connected with said contact, a plurality of electric gaseous discharge lamps having a substantially fixed breakdown potential within said tube and connected across different fixed fractions of said potentiometer, said fractions being so graduated that successive lamps light up as a linear function of the voltage drop in said potentiometer, said lamps being located behind a translucent portion of said tube and arranged sequentially whereby the illumination of successive lamps gives the-illusion of an increasing line of light, a scale on the face of said tube to calibrate said line of-light, a resistance between each individual lamp and said potentiometer, said resistances being so varied in value that the current through each of said lamps is substantially the same when all of said lamps are operating, an impedance connected in series with said potentiometer, and means including a switch located in the wall of said tube to shunt said potentiometer at will to change the voltage range of-said device.

TED E. FOULKE. 

